/Engine/Plugins/FX/Niagara/Source/NiagaraEditor/Public/NiagaraNode.h
Basically routes the pin through the parameter map builder so that it looks like a regular pin. Handles visiting the node connected as well to the input pin.
virtual void RegisterPassthroughPin ( [FNiagaraParameterMapHistoryBuilder](API\Plugins\NiagaraEditor\FNiagaraParameterMapHistoryBuild-) & OutHistory, [UEdGraphPin](API\Runtime\Engine\EdGraph\UEdGraphPin) * InputPin, [UEdGraphPin](API\Runtime\Engine\EdGraph\UEdGraphPin) * OutputPin, bool bFilterForCompilation, bool bVisitInputPin ) const